Removal of naphthenic acids from hydrocarbon oils



July 2, 1935. F. M. ROGERS 2,007,146

REMOVAL OF NAPHTHENIC ACIDS FROM HYDROCARBON OILS Filed Dec. 12, 1 928 Patented July 2, 1935 PATENT OFFICE,

REMOVAL or NAPHTHENIC Aoms FROM nrnnocmon OILS Francis M. Rogers, Whiting,

Standard Oil Company,

poration of Indiana Ind., assignor to Whiting, Ind., a cor- Applicatlon December 12, 1928. Serial No. 325,504

12 Claims.

This' invention relates to the removal of naphthenic acids from hydrocarbon oils, and will be readily understood from the following description in conjunction with the accompanying drawing, which illustrates diagrammatically a suitable apparatus for effecting such removal.

Referring to the drawing, the numeral I0 designates a pipe-still coil, located in a setting II and adapted to be heated by suitable burners I2.

The inlet l3 of the coil I0 is provided with a suitable pump (not shown) for forcing the oil through the coil. The inlet l3 may be supplied with the oil from suitable heat exchangers (not shown), whereby the oil is preheated to a substantial extent. The outlet ll of the coil l0 leads into an enlarged chamber or flash drum l5. At an intermediate point and preferably near the outlet H, the coil I0 is provided with a pipe l6 adapted to supply steam into the coil for the'purpose of assisting in vaporizing the oil passing therethrough.

The flash drum I5 is provided at its base with a tar outlet IT. From the upper end of the flash drum II a vapor outlet It leads into the base of a bubble tower l9 which contains a substantial number of bubble cap plates through which the vapors ascend. As shown in the drawing, the bubble cap plates constitute two separate groups; the group constitutedby the three lowest plates being hereinafter called the alkali plates" and the group constituted by those above the three lowest plates being hereinafter termed the entrainment plates".

An inlet leads into the tower for the purpose of supplying caustic solution to the uppermost of the alkali plates whiTe anlnlet 2| leads into the tower above the entrainment plates for the purpose of supplying cooling medium thereto. The lowermost entrainment plate. is not provided with the usual overflow to the plate beneath, but an 40 exterior by-pass 22 is provided whereby liquid from said lowermost plate is passed into the base of the tower. The tower is provided at its base with a draw-oil pipe 23 and at its upper end with a vapor pipe 24 which leads into an intermediate point of a fractionating column 25.

The fractionating column may suitably be of the bubble cap type, and is provided at the bottom with a draw-oil. conduit 26 and a perforated pipe 21 for supplying open steam and at its upper end with a vapor pipe 28 which leads into an intermediate point of another fractionating column 29.

The fractionating column' 29 is provided at its base with a liquid draw-oil? conduit 30 "and a perforated pipe 3| for supplying open steam into the column, and at its upper end with a vapor outlet 32 which leads to a condenser 83 of conventional type. v

At their upper ends, the columns 25 and 29 are provided with liquid inlets 34 and 35 for the purpose of supplying cooling medium into said column.

The method of conducting the process is as follows:

The oil containing naphthenic acids is .supplied by the inlet l3 to the coil Ill. As indicated above, the incoming oil is preferably preheated by heat exchangers and may have a temperature between 250 and 350 F. In passing through the coil ill the oil is rapidly heated to a high tempera- 1 ture sufficient to volatilize the desired percentage of the oil. This temperature may be in the cracking range since the time of. exposure is insumcient to cause any appreciable cracking or deterioration of the lubricating qualities of the oil. A cer-' tain amount of steam is preferably introduced by the pipe I6 into the coil l0 so that the desired vaporization may be obtained without excessive temperatures. The heated oil, steam and vapors pass into the flash drum l5. The unvaporized oil or tar is withdrawn by the outlet ll while the steam and vapors pass into the bottom of the bubble cap tower l9 and pass upwardly through.- the plates thereof. 1

A solution of caustic alkali is supplied to the caustic alkali plates by the pipe 20. Caustic soda or caustic potash may be employed, but it is preferred to employ the former, owing to its cheapness and its lower melting point. The highly heated vapors pass upwardly through the caustic alkali plates and substantially evaporate the water therefrom. The caustic alkali remains molten and descends from plate to plate to the bottom of the tower. In passing upwardly through the caustic alkali the oil vapors are substantially deprived of their naphthenic acid content. These vapors then pass upwardly through the entrainment plates. A. small amount of reflux is caused to flow down'these plates and passes by the pipe 22 from the lowermost en- 1 trainment plate into the base of the tower N. This reflux may suitably be for-med by supplying a suitable amount of gas oil or other suitable oil to the uppermost plate. It will be understood, however, that the reflux may be produced in any 60 other suitable way, for example, bypassingcooling medium through a coil in the upper part of the tower. A small amount of reflux, excess caustic alkali and alkali naphthenates. etc., are

withdrawn by'the outlet 23. The vapors pass by I pipe 24 into an intermediate point of the fractionating column 25.

Reflux is formed in the column 25 by supplying distillate oil thereto by the pipe 34. It is to be understood that the reflux may be produced in any other known or suitable manner. The refiux oil is stripped in the lower part of the column 25 by open steam introduced by the pipe 21. Lubricating oil of desired quality is withdrawn by the pipe 26, the quality of the oil being controlled by controlling the supply of steam by the pipe 21. The vapors pass by pipe 28 to an intermediate point of the column 29, which is operated in a manner similar to that described in connection with the tower 25, a lighter lubricating oil being withdrawn by the outlet 30. The vapors pass from the column 29 and may be condensed in any suitable manner, for example by condenser 33.

The invention will be readily understood from the following specific example.

Smackover crude oil having a gravity of about 17 API and a naphthenic acidity equivalent to 0.5 mg. KOHper gram of oil is fed to the pipe still at the rate of about 2000 gallons per hour. This oil has been preheated to a temperature of about 300 F. About 5000 lbs. of steam are supplied per hour by pipe IS. The steam and partially vaporized oil leave the pipe still at a temperature of about I50" F. and substantially at atmospheric pressure. Under these conditions, about 27% of tar is separated in the fiash drum i5 and withdrawn by the outlet l'l.

A 43% solution of caustic soda is fed at the rate of 2 gallons per hour by the pipe 20 onto the caustic alkali plates. Since the temperature here is about 700 F., the water is largely evaporated and the caustic soda is maintained in a thoroughly molten condition. Substantially all the naphthenic acids are retained by the caustic soda.

A small amount of gas oil is supplied to the entrainment plates by pipe 2| so that a small amount of heavy reflux, suitably about 1% of the crude oil supplied, is formed in the entrainment section and passes by pipe 22 to the base of the tower. This reflux prevents sodium hydroxide or sodiumcompounds from being carried over by the vapors into the tractionating column 25. This procedure is adopted in order to reduce as far as possible the amount of liquid oil on the caustic plates, as molten caustic soda exerts a strong carbonizing eflect at the temperatures involved.

The column 25 is operated to yield by the outlet 20 a lubricating oil having a viscosity of about 350 sec. Saybolt at F. and a flash of 390 F. A: indicated above, the column 25 is operated by supplying a controlled quantity of gas oil, or the like, by the pipe 34 and by supplying a controlled quantity 0! steam by the pipe 21. The acidity of this oil is equivalent to 0.03 mg. KOH per gram of oil. The yield of this oil is about 38% of the original crude oil. This lubricant may suitably be finished by agitating with about 0.2 lbs. of 89% sulfuric acid per gallon of oil, the sludge separated and the sour oil agitated with about 5% or its weight of finely divided Iuller's earth and then filtered tree from solids. The resulting oil has an acidity of 0.04 mg. KOH per gram of oil and a color'oi 1 to 2 P. Tag. Robinson scale. Vapors at a temperature of about 400 F. pass by the pipe 23 to the column 29. This column is also operated by supplying a controlled amount or gas oil by the pipe 35 and a controlled amount of steam by the pipe 3|. The oil withdrawn by the pipe 30 has a viscosity of about 50 sec. Saybolt at 100 F., a fiash of about 280 F. and an acidity of 0.02 mg. KOH per gram of oil. The yield of this oil is about 5% of the crude oil.

The condensate from the condenser 33 is a gas oil and amounts to about 29% of the original crude.

Although the invention has been described in connection with the details of a specific example thereof, it must be understood that such details are not intended to be limitative of the invention, except in so far as included in the accompanying claims.

What I regard as new, and Letters Patent, is:

l. The method of removing naphthenic acids from hydrocarbon oil, which consists in vaporizing said oil and passing the vapors through molten caustic alkali.

2. The method of removing naphthenic acids from hydrocarbon oil, which consists in vaporizing said oil and passing the vapors through molten caustic soda.

3. The method of removing naphthenic acids from hydrocarbon oil, which consists in vaporizing the said oil, passing the vapors upwardly through a tower, supplying caustic alkali within said tower and through at least one pool of molten caustic alkali in molten, substantially anhydrous form, and causing same to flow downwardly therethrough.

4. The method of removing naphthenic acids from hydrocarbon oil, which consists in' vaporizing the said oil, passing the vapors upwardly through a tower and through at least one pool of molten sodium hydroxide, supplying sodium hydroxide within said tower in molten, substantially anhydrous form, and causing same to fiow downwardly therethrough.

5. The method of removing naphthenic acids from hydrocarbon oil, which consists in vaporizing said oil, heating the vapors to a temperature above the melting point of sodium hydroxide, passing said vapors upwardly through a tower and through at least one pool of molten sodium hydroxide, supplying sodium hydroxide solution into said tower, whereby substantially all the water is evaporated therefrom and the sodium hydroxide maintained in molten condition, and causing the said' molten sodium hydroxide to pass downwardly through said tower in countercurrent to the ascending vapors.

6. The method of removing naphthenic acids from hydrocarbon oil, which consists in vaporizing said oil and passing the vapors upwardly through a tower and through one pool of molten caustic soda, maintaining molten caustic soda in the lower part of said tower and producing a small amount of refiux in the upper part of said tower thereby preventing entrainment of sodium compounds.

7. The method of removing naphthenic acids from hydrocarbon oil, which consists in vaporizing said oil, supplying the vapors to the base of a tower and causing the same to ascend therethrough, causing molten caustic soda to descend through the lower part of said tower, producing a small amount of reflux in the upper part of said tower for the purpose of removing entrained sodium compounds from the vapors and supplying said reflux and entrainment directly from the lowermost part of the upper section to the base of the tower.

8. The method of removing naphthenic acids desire to secure by dium compounds, supplying said reflux and entrained compounds directly into the base of said tower, by-passing the caustic soda section, withdrawing reflux and sodium compounds from the base of the tower, withdrawing vapors from the top oi said tower, and subjecting them to fractional condensation.

9. The method of removing naphthenic acids from hydrocarbon oils, which comprises vaporizing said oil, heating the vapors to a temperature above the melting point of caustic alkali, passing said vapors upwardly through a tower, supplying an aqueous solution of caustic alkali into said tower, whereby substantially all the water 01 said solution is evaporated and the substantially anhydrous caustic alkali maintained in molten condition, and forming a pool of said caustic alkali and causing the ascending vapors to pass therethrough.

10. The method of removing naphthenic acids from hydrocarbon oil, which comprises vaporizing said oil, heating the vapors to a temperature above the melting point of sodium lrvdroxide,

passing said vapors upwardly through a tower,

supplying aqueous sodium hydroxide solution into said tower, whereby substantially all the water of said solution is evaporated and the sodium hydroxide remaining is melted, and maintaining a pool of molten sodium hydroxide and causing the ascending vapors to pass therethrougli.

11. The method of removing naphthenic acids from hydrocarbon oil which comprises maintaining a body oi molten substantially anhydrous caustic alkali, vaporizing said oil, and passing the oil vapors through said molten caustic alkali body.

12. The method of removing naphthenic acids from hydrocarbon oil which comprises passing said oil in vaporous form through a body of molten alkali, said oil vapors being heated to a temperature above the melting point of the alkali whereby said alkali is maintained in molten condition.

FRANCIS M.- ROGERS. 

